Author(s):
Sudershan Mishra, Babita Joshi, Prithwiraj Dey, Himanshu Pathak, Neha Pandey and Aarzoo Kohra
Abstract:
The evolution of organisms capable of oxygenic photosynthesis paralleled a long-term reduction in atmospheric CO
2 and the increase in O
2. Consequently, the competition between O
2 and CO
2 for the active sites of RUBISCO became more and more restrictive to the rate of photosynthesis. In coping with this situation, many algae and some higher plants acquired mechanisms that use energy to increase the CO
2 concentrations (CO
2 concentrating mechanisms, CCMs) in the proximity of RUBISCO. The CCM improves photosynthetic performance by raising the CO
2 concentration at the site of ribulose-1,5-bisphos-phate carboxylase/oxygenase (Rubisco), simultaneously enhancing carbon fixation and suppressing photo-respiration. Active inorganic carbon (Ci) uptake, Rubisco sequestration and inter-conversion between different Ci species catalyzed by carbonic anhydrases (CAs) are key components in the CCM, and an array of molecular regulatory elements is present to facilitate the sensing of CO
2 availability, to regulate the expression of the CCM and to coordinate interplay between photosynthetic carbon metabolism and other metabolic processes in response to limiting CO
2 conditions. Although the molecular components underpinning the above metabolics is very much clear, the related regulatory pathways still need to be elucidated.
Sudershan Mishra, Babita Joshi, Prithwiraj Dey, Himanshu Pathak, Neha Pandey and Aarzoo Kohra. CCM in photosynthetic bacteria and marine alga. J Pharmacogn Phytochem 2018;7(6):928-937.